ByZaib-Ur-Rehman

Lecturer Department of Poultry Science

PMAS, Arid Agriculture University, Rawalpindi, Pakistan

What is respiratory system?

“The respiratory system is the anatomical system of an organism that introduces respiratory gases to the interior and performs gas exchange”

Respiratory system of poultry comprise of

1. Nasal opening

2. Nasal passage

3. Trachea

4. Bronchi (bronchus)

5. Lungs

6. Air sacs

Differences between the respiratory system of poultry and mammals Tracheal rings are complete in case of birds

The organ of phonation (syrinyx) is located at the bifurcation of trachea rather than near pharynx

The lungs are fixed in position and can not contract and expand in the respiration

Air sacs are present in the birds while absent in case of mammals. The air sacs are extended to the bones known as pneumatic bones. These structures have the ability to contract and expand with respiration

Diaphragm is absent in birds

TRACHEA Trachea conducts the air from nasal cavity and mouth

to the bronchus or bronchi Causes the warming and moistening of air Causes the screening of dust and foreign material It also provides the local immunity

1. By filtering or screening the dust particles with thehelp of cilia

2. Mucous3. Production of immunoglobin (Ig A) that are

antibodies

The trachea after entering into the body bifurcatesinto two structures known as bronchi (Rightbronchus, left bronchus)

BRONCHI Bronchial system of bird consists of three orders of

branching before the gas exchange units are reached

1. Primary bronchus

2. Secondary bronchus

3. Tertiary bronchus (Para bronchi)

4. Peri perabronchial mental

PRIMARY BRONCHI The primary bronchus arises from the bifurcation trachea.

It has two parts.

1. Extra pulmonary primary bronchus

2. Intra pulmonary primary bronchus

Part of the bronchus outside the lung is known as extrapulmonary primary bronchus

Part within lungs is known as intra pulmonary primarybronchus

Primary bronchus is made up of circular cartilage rings andhas a well developed layer of smooth muscles whichcontrol the diameter or size of the bronchus

SECONDARY BRONCHI The bronchus arising from the primary bronchus is known

as secondary bronchus. In most of the birds secondarybronchi are arranged into four groups.

1. Medioventral

2. Mediodorsal

3. Lateroventral

4. Laterodorsal

Cervical, clavicular, and cranial thoracic air sacs arise fromthe medioventral group of secondary bronchi

Caudal, thoracic and abdominal air sacs are derived frommediodorsal and lateroventral group of secondary bronchi

TERTIARY BRONCHI

The tertiary bronchi (Para bronchi) are derived from themultiple ramifications of secondary bronchi. These are longnarrow tubes that display a high degree of anastomosis (Theconnection of separate parts of a branching system to form anetwork, as of leaf veins, blood vessels, or a river and itsbranches)

The para bronchi give rise to a specific structure known as atriawhich is out pocketing on the surface of Para bronchi

It give rise to extensions known as infundibuli The infundibuli gives rise to final extensions known as air

capillaries The atria, infundibuli, and air capillaries collectively leads to the

formation of a gas exchange unit peri Para bronchial mental. Theblood capillaries make close contact with peri para bronchialmental and thus the exchange of gases takes place between theblood present in the blood capillaries and air present in the aircapillaries

In most of the birds two kinds of Para bronchi arepresent

1. Paleopulmonic Para bronchi

2. Neopulmonic Para bronchi

The Para bronchi located towards the cranium air sacsare known as paleopulmonic para bronchi

Those located towards the posterior or caudal air sacsare known as neopulmonic para bronchi

AIR SACS The birds have 9 air sacs.

1. One clavicular

2. Two cervical

3. Two anterior thoracic/ cranial

4. Two posterior thoracic/ caudal

5. Two abdominal

The air sacs are the continuation of the secondary bronchi Air sacs are made up of thin walled structure which

comprise of simple squamous epithelium and a thin layerof connective tissue

The walls of air sacs are poorly vascularized (poor bloodsupply) due to which non significant exchange of gas takesplace

The air sacs are extended to certain bones and make thempneumatic in nature

The air sacs are extended to the cervical vertebrae, thoracicvertebrae, ribs, sternum, humerus, pelvis, head, and bodyof femur

The air sacs are responsible for providing the space duringthe respiratory cycle and there by function to increase thepulmonary ventilation

MECHANISM OF RESPIRATION The respiratory mechanism is composed of two

processes

Inspiration

Expiration

Inspiration or Inhalation:

Inspiration is a process during which the air is takenup by the bird and processes in the lungs

Process is active process because it consumes energywhile in case of mammals this process is passive

Expiration or Exhalation

The discharge or removal of air into the environment isknown as expiration or exhalation

This process is passive in nature in birds while active incase of mammals

As the birds are lacking in diaphragm but so theprocess of respiration depends upon thoracic,abdominal, and cervical muscles

During the process of inspiration the inspiratorymuscles contract ultimately leading to the increase ininternal abdominal thoracic volume and pressuredecreases

Due to this process the pressure in the air sacs is reducedand air from external environment moves towards the airsacs through neopulmonic para bronchi while towardscranial air sacs through paleopulmonic para bronchi

During the process of respiration the exchange of gasestakes place in the mental of neopulmonic para bronchi andpaleopulmonic para bronchi

The oxygen moves towards the blood from air capillarieswhile carbon dioxide moves towards the air capillaries fromgut

The exchange of gases depends upon the difference ofpartial pressure of particular gas either in air capillaries orblood stream present in the blood capillaries

The blood capillaries and peri para bronchial mental arearranged in a specific type of arrangement known as crosscurrent arrangement

In this type of arrangement the air capillaries and bloodcapillaries are present at right angle to each other due towhich maximum exchange of gases takes place by diffusion

In the process of respiration the respiratory musclescontract leading to an increase in the intrathoracoabdominal pressure which ultimately generates thepressure on air sacs thus leading to expiration of inhaled air

The air present in the caudal air sacs is passed through theneopulmonic para bronchi

The air then enters the cranial air sacs while the air presentin the cranial air sacs is removed and the air entering fromthe caudal air sacs is removed during the secondrespiratory cycle

THERMOREGULATION The birds like mammals are homoeothermic in nature

because they tend to maintain the temperature of deeplyseated organs like brain, liver, heart, intestine etc. Inhomeothermic animals the amount of heat produced bythe muscular exercise and metabolic activity like oxidationof glucose is equal to the amount of heat loss from theanimal to its environment. The heat is lost to theenvironment by the process

Radiation

Conduction

Convection

Evaporation/panting

Radiation

“The heat exchanged by the radiation involves thetransfer of heat by electromagnetic wave and consist ofheat transfer within both the visible and infrared portionof spectrum”

Conduction

“Loss of heat by this process involves the direct transferof heat from the animal body surface to the air. The lossof heat by the process of conduction is very low becausethe thermal conductivity of skin and subcutaneoustissue is also low”

Convection:

“Heat loss by the process of convection takes place dueto direct contact of air or any other material with skin ofanimal. The heat loss by this process depends upon thevelocity of air as well as the temperature of air. The heatloss by this process also depends upon the surface area ofbody in contact with air”

Evaporation\panting:

“The birds do not contain the sweat glands due to whichthe loss of heat from skin by the form of evaporation isnot possible. On the other hand the heat loss occur byevaporation from the most lining of respiratory tract aswell as the tongue”